1. Field of the Invention
The present invention relates generally to an improved heat pipe structure, and more particularly to a heat pipe structure, which can be activated at low temperature to keep operating at normal temperature to enhance the performance. Moreover, the assembly applicability is enhanced to lower the assembling cost.
2. Description of the Related Art
A heat pipe has an evaporation end and a condensation end and has an internal vacuumed chamber. A working fluid is contained in the chamber. The chamber is in a vacuumed state so that the boiling point of the working fluid is relatively low. The heat is transferred by means of the liquid-vapor phase change of the working fluid in form of latent heat. At the evaporation end, the working fluid is evaporated to carry away a great amount of heat from a heat source in form of evaporation latent heat. The vapor of the working fluid is filled up in the vacuumed chamber and condensed into liquid at the condensation end to release heat. The liquid working fluid flows back to the evaporation section under the capillary attraction provided by the capillary structure in the chamber for the next circulation of phase change. Accordingly, the vapor-liquid circulation of is continued to effectively transfer the heat generated by the heat source to a remote end for heat exchange.
In general, the working fluid contained in the heat pipe is pure water. This is because pure water is easily available and the specific heat and latent heat in the physical properties of pure water are relatively high. That is, more heat is absorbed and carried away per unit mass. The chamber of the heat pipe is in a vacuumed state. However, this will not affect the solidification temperature of pure water. When a heat pipe with pure water serving as the working fluid is used outdoors in an environment with an environmental temperature under 0 degrees, the working fluid in the heat pipe will be solidified into ice. Under such circumstance, the working fluid will be unable to provide heat transfer effect. As a result, the temperature of the electronic device or relevant apparatus that needs heat dissipation will abruptly rise to affect the electronic components in the electronic device. This will affect the function of the electronic device or relevant apparatus or shorten the lifetime thereof.
Therefore, in general, when the heat pipe is used outdoors in an environment with an environmental temperature under 0 degrees, methyl alcohol is contained in the chamber of the heat pipe as the working fluid. However, the specific heat of methyl alcohol is lower than that of pure water. Therefore, in a normal-temperature condition, the heat conductivity or maximum heat capacity of the heat pipe with methyl alcohol as the working fluid is lower than that of the heat pipe with pure water as the working fluid. Accordingly, in order to achieve optimal heat conductivity in both normal-temperature condition and low-temperature condition, it is necessary to increase the number of the heat pipes so as to provide best heat dissipation effect. Moreover, it is often necessary to co-use both pure water heat pipe and low-temperature heat pipe. It is troublesome to assemble these heat pipes so that the assembling cost is increased. In addition, after assembled, the assembly can be hardly applied to all the devices or apparatuses. Therefore, the applicability is lowered.
According to the above, the conventional heat pipe has the following shortcomings:
1. It is hard to assembly the heat pipes.
2. The assembling cost is increased.
3. The applicability of the assembly is lowered.